1. Field of the Invention
The present invention relates to an apparatus and method for sensing a state of a movable body, and more particularly to a non-contact type state sensing apparatus and method.
2. Description of the Related Art
In general, movable bodies such as ships, airplanes and cars, have been provided with navigation systems for determining positions of the movable bodies and providing an optimum path to a desired destination. In order to determine positions of the movable bodies and provide an optimum path to a destination, the navigation systems must know the speeds of the movable bodies. Accordingly, the navigation systems have been provided with speed sensors for sensing the speeds of the movable bodies.
In general, speed sensors used in navigation systems can be classified into contact type speed sensors, which directly sense speed information by means of an odometer, and non-contact type speed sensors, which calculate a speed by means of an accelerometer.
In the contact type speed sensors, since an error of an odometer does not increase according to passage of time, a speed error is maintained at a constant level. However, in order to realize the contact type speed sensor, a circuit having speed information, which is installed inside of the car, must be connected with a speed sensor outside of the car. Therefore, the contact type speed sensor requires a complicated and costly process for installing a measurement device including the speed sensor. Further, since odometer types and circuit structures are different according to the kind of car, the installation processes may be different according to the kind of car. Therefore, additional costs may be incurred.
Since such wire connection is not necessary in the case of the non-contact type speed sensor, the installation process is not only simple, but also there are no additional costs. However, since the non-contact type speed sensor calculates a speed by integrating an output of an accelerometer, any error of the accelerometer is also integrated. Therefore, a speed error increases according to passage of time.
Further, a recently improved navigation system provides various services such as a service of “guiding a car to an adjacent gas station according to a fuel state of the car”, or a service of “guiding a car to an adjacent gas station after sensing whether trouble exists or not in an engine”, or a service of “enabling a car to be receive prompt service by wirelessly informing an adjacent gas station of a current position and abnormal state of the car”. However, even if most of the information has been provided from the existing dashboard, sensors for sensing the current state of the movable bodies must be installed on each corresponding device of the movable bodies in order to sense the state of the movable bodies. Therefore, the costs increase.